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, TELBPHONIU RECEIVER. N0.295.8O4'. Patented Mar 25, 1884.

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OHARLESA. RANDALL, OF NEW YORK, NLY.

'TELEPHONIC RECEIVER.

SPECIFICATION forming part of Letters Patent No. 295,804, dated March 25, 1884.

' Application filed May a, 1883. (No model.)

To all whom it may concern.-

Be it known that I, CHARLES A. RANDALL, a citizen of the United States, residing at New York, in the county and State of New York,

have invented new and useful Improvements in Telephonic Receivers, of which the following is a specification.

This invention relates to an improvement in the type of telephone-receivers shown-in my Patent N 0. 235,021, dated November 30, 1880,

in which a diaphragm carries a centrally-projecting soft-iron core which extends loosely into a hollow helix and is acted upon to vibrate the diaphragm by electric currents traversing the helix, the tip of the core being close to a permanently charged stationary magnet, the magnetic action of which upon said core is alternately re-enforced and coun- In the patent above teraeted by the currents. referred to, the core, which is carried by the diaphragm, is magnetized only by the inductive eiiect of the helix and the stationary magnet.

One object of the present invention is to give the receiver a more sensitive character by charging the movable core by contactwith a' permanent magnet, -so that there will be a much greater normal attraction between it and included in the circuit when thereceiver is taken in hand for use.

In the accompanying drawings, Figure l is a side view of the telephonic receiver constructed according to my invention. Fig. 2 is a section of the instrument in the plane of the diameter of the helix and longitudinal center of the permanent magnet. Fig. 3 isa detached perspective view of the permanent magnet.

Fig. 4 is a sectional view" of a modified form of instrument in a plane similar to that of Fig. 2.

The letter A indicates a permanent magnet of horseshoe shape, having one of its holes, as

into their most effective relation.

placed the diaphragm 0, outside of which is arranged the mouth-piece D, in the usual manner. To the center of the diaphragm is secured one end of a projecting soft-iron core, E, which extends through the opening in the flattened portion a of the magnetleg, and has its tip close to the opposite pole of the magnet. Behind the flattened pole a is secured a hollow helix, F, which surrounds the core E, and is to be connected in the receiving-circuit when the instrumentis in use in substantially the ordinary manner. In the opposite pole of the magnet from the flattened pole a is arranged an adjustablesoft-iron screw, G,

which is magnetized by its contact with the magnet, and may have its tip adjusted toward or from the tip of the core E, for the purpose of bringing the operative poles of themagnet It will now be readily seen that the core E and screw G,

being both magnetized by contact with the permanent magnet, will have such an attraction for each other that the elastic diaphragm C will be normally bowed inwardly with considerable'force, and when 'the electrical impulses of one polarity traversing the helix neutralize the normal magnetism of the core and,

create a new polarity of. the tipof the core the resilience of the diaphragm and the repelling magnetism of G will cause the diaphragm to make an outward half-vibration of certain amplitude and force, and when the current is reversed it will perform another half-vibration back or in an opposite direction to the first with a force much greater than that of the simple attraction of the two poles for each other, from the fact that this inward half-vibration results from the attraction between two magnetic poles of opposite polarity reenforced by the polarization by the current flowing over thehelix, instead of the attraction simply of one magnetic pole for an unmagnetized core. In Fig. 4 the core is left oii the diaphragm, and the polar screw G is extended into the helix, and may be adjusted in. proper having in its lower portion a chamber, h,

which is closed by a cap, h. To the outer surface of this cap are secured two bindingposts, 11 and 13, and through said cap extends a metallic rod, 70, which is driven inwardly by a metallic spring, which surrounds the rod and has one end bearing against the pin k" therein, and its other end bearing against the inner surface of the cap if, the inward movement of the rod being limited by a shoulder, k ,.which strikes the outer surface of the cap. Nearits inner end an insulating-plate, Z, is

let into the rod 70, and against said rod bears the tip of a metallic finger-spring, m, the opposite end of which is secured to the inner surface of the cap h. The tip of this spring m bears against the metallic portion of the rod Zc just below the insulating-plate Z when the rod is driven inward by its spring, but will bear against said insulating-plate Z when the rod is drawn outward, as would be the case when the instrument is suspended by the ring on the outer end of the rod and its weight rests upon and compresses the spring k. One of the wires, to, which leads from the helix and through the handle, is connected with the binding-post Z, and the other wire, 10, is connected with the finger-spring m, while the binding-post t" is connected with the metallic spiral spring 70, which bears against the metallic pin k and the red It.

It will now be seen that when the instrument is removed from its usual supporting hook and the rod is forced inward by the spring 70' an electrical current flowing over the main line circuit to the binding-post i will pass over the wire m, the helix F, wire w, finger-spring m, rod is, pin it, spring 7c, and the connection bet-ween it and bindingpost i, and from this binding-post off again on the main line, the. instrument being thus in eluded inthe main circuit.

When the instrument is not in use and is suspended by the rod 70, said rod will be drawn outward, and the tip of the finger-spring m will rest upon the insulating-plate Z, so that the circuit will be broken and the helix cut out.

It is very desirable that as little resistance as possiblebe included in the main line, and

moval from the main circuit of the helices of all receiving-instruments which are not in actual use. A further advantage of these antomatic devices is that when the devices are not in use they are placed out of danger of injury by lightning.

Having thus described my invention, what I claim is 1. In a telephonic receiver, the combination of a permanent magnet having one of its poles formed into a disk integral therewith, and provided with a rim or raised edge forming a support for the vibratory diaphragm, an elastic or vibratory diaphragm secured thereto and arranged to be acted on inductively, and a helix arranged to vary and control the inductive action of the permanent magnet upon the elastic or vibratory diaphragm, substantially as described.

2. In a telephonic receiver,the combination, with the permanent magnet A, having one of its poles flattened or laterally extended and centrally perforated, of the diaphragm secured to the outer margin of said flattened pole, the core projecting from the diaphragm through the opening in the flattened pole and close to the other pole, and the helix loosely surrounding said core, substantially as described.

3. The combination, in a telephonic receiver, of a permanent magnet having one of its poles formed into a disk integral therewith, and having a raised rim or edge for supporting the vibratory diaphragm, an elastic or vibratory diaphragm supported thereon, a softiron core or extension attached to or in contact with the other pole of the permanent magnet, and a helix surrounding and adapted to influence such soft-iron core or extension, the thus formed operative poles of the magnet being in magnetically operative proximity to each other, and the helix being arranged to vary and control their magnetic action on each other and the vibratory or elastic diaphragm, substantially as described.

4.. The combination, with the helix and the handle, of the spring-actuated rod 70, provided with the insulating-plate Z, the finger-spring bearing against said rod and connected with the helix, and the binding-posts connected, respectively, with the helix and the said rod, substantially as described.

In testimony whereof I have hereunto set my hand in the presence of two subscribing witnesses.

(1. A. RANDALL.

WVitn esses:

J. W. HUeHns, WV. J. OAHOONE. 

